Developer · Free Tool
Number Base Converter
Convert numbers between Binary, Octal, Decimal, and Hexadecimal instantly, with all four bases shown at once.
Binary = base 2 · Octal = base 8 · Decimal = base 10 · Hexadecimal = base 16
About this tool
Type a number into any one of the four fields — Binary, Octal, Decimal, or Hexadecimal — and the other three update instantly, so you always see all four representations of the same value side by side. Invalid digits for the selected base (like an 8 in a binary field) are flagged immediately.
Base conversion comes up constantly in low-level programming, networking, and debugging — reading a hex color or memory address, decoding octal file permissions, or checking what a binary flag field actually represents in decimal. This tool skips the mental math and shows the full picture at once.
Common uses
- Convert a hexadecimal color, memory address, or error code to decimal to reason about its actual value
- Decode Unix file-permission octal values (like 0755) into what they actually allow
- Check a binary bitmask or flags field against its decimal or hex equivalent while debugging
Frequently asked questions
Why does decimal 255 equal hexadecimal FF?
Hexadecimal is base 16, using digits 0-9 and A-F. FF means 15×16 + 15 = 255 — it's the largest two-digit hex value, which is why it shows up constantly as a maximum (like 255 for a color channel or an 8-bit byte).
What are octal file permissions like 0755 actually encoding?
Each octal digit (base 8, digits 0-7) represents three permission bits — read, write, execute — for owner, group, and others respectively. 0755 decodes to rwxr-xr-x: the owner gets full access, everyone else gets read and execute only.
Is there a limit to how large a number this handles?
The tool uses JavaScript's BigInt internally, so it comfortably handles very large integers beyond the normal 53-bit safe integer limit — useful for 64-bit values that show up in low-level programming.
Is my data uploaded to a server?
No. This tool runs entirely in your browser using JavaScript — nothing you type is transmitted, logged, or stored anywhere. You can even use it offline once the page has loaded.